In many laser projectors, light beams of the primary colors RGB are directed onto a projection surface by a two-dimensional deflection mirror (so-called scanner mirror). By appropriate movement of the scanner mirror and a correspondingly coordinated time-intensity variation of the laser sources, an image is generated on the projection plane (“flying spot method”).
Because of cable lengths, impedances and rise times related to the component, delays develop between the optical output signal (laser intensity) and the location of the laser image spot on the projection plane. The result is image distortion.
When several lasers are used (generally corresponding to several colors, or also the same color) in a design concept with intentional local image spot offset of the laser beams with a fixed mirror, image distortions on the projection level occur related to production or the design concept, if the time/location behavior of the intensity signals of the different light beams deviate from each other. In order to obtain good image quality, time agreement of the optical output signal and mirror movement for each laser image spot is required in the projection plane.
The problem of the aforementioned image distortions has thus far been solved by using high clock frequencies of the digital control electronics, in order to delay the corresponding laser control signals in the smallest possible steps. Delay of the digital voltage signal for laser control leads to a delay of the intensity signal of the laser by the same time unit. The smallest unit of digital delay corresponds to the time of the system clock of the control electronics. If a clock frequency is used that lies on the order of magnitude of the exposure time of the shortest exposed pixel, an error in time agreement on the order of half a pixel width can then occur (image unsharpness). To avoid this error in time agreement, a distinctly higher clock time is ordinarily used than the duration of the shortest exposed pixel. This means that the calculation and memory demands are significantly increased. The need for comparatively expensive control electronics follows from this.